The invention relates to a drill hole measuring device comprising: a frame; at least one sensor; an elongated transmission element connected to the sensor; at least one transfer device, by which the transmission element can be moved longitudinally in at least one direction for moving the sensor in the drill hole.
The invention also relates to a rock drilling unit comprising: at least one feeding beam; at least one rock drilling apparatus, which is movable with respect to the feeding beam; and at least one measuring device for measuring drill holes, the measuring device comprising: a frame; at least one sensor that can be arranged in a drill hole; an elongated transmission element connected to the sensor; and at least one transfer device, by which the transmission element can be moved longitudinally for moving the sensor in the drill hole.
In measuring the straightness and dimensions of downward-oriented drill holes it is typical that a sensor, supported by a cable, is lowered into the drill hole. The measuring device may comprise a winch, by which the sensor can be lowered and lifted in the drill hole. Alternatively the measuring device can be arranged in connection with the drilling boom, whereby the sensor is inserted into the drill hole by means of a suitable transfer device and a flexible transmission element, such as a hose or a rod. A device of this kind is disclosed in U.S. Pat. No. 6,460,630. Prior art solutions, however, have a draw-back that the handling of the sensors is difficult and while being transferred the sensor is subjected to knocks and mechanical stress. Sensitive sensors may get damaged and both measuring inaccuracy and extra costs may occur.